The present invention relates to a process for producing a part of a torque converter and, more particularly, to a process for forming a torque converter part having slits, such as an inner core or an outer shell of a torque converter.
FIG. 1 illustrates a portion of a conventional torque converter, particularly an inner core and an outer shell of the torque converter. As will be seen from this FIG., the torque converter has an inner core 1, an outer shell 2 and a circumferential row of blades 3 interposed between the inner core 1 and the outer shell 2. The inner core 1 and the outer shell 2, therefore, have toroidal form with the inner core, having slits formed therein for the purpose of receiving the blades 3. FIG. 2 is a perspective view of the inner core 1 and the blades 3 which are assembled together. The inner core 1 has slits 5 which receive fixing tabs 4 on one end of the blades 3. The tabs 4 are folded onto the inner core 1 so that the blades 3 are fixed to the inner core 1.
Conventionally, the slits in the inner core and the outer shell have been formed in a manner which will be explained below with specific reference to FIG. 3.
A metal sheet 10 as a blank is prepared and is punched as shown in FIG. 3(a) and the peripheral portion of the hole formed by punching is removed as shown in FIG. 3(b) whereby a work product 11 as shown in FIG. 3(c) is obtained. The work product 11 is then subjected to deep drawing or spinning so that a toroidal inner core 12 is obtained as shown in FIG. 3(d).
Slitting is then effected on the inner core 12 by a press on the toroidal inner core 12 as shown in FIG. 3(e). After the In slitting, burrs 14 are inevitably formed on the punch-exit side of the inner core 12. In other to remove these burrs, therefore, it has been necessary to conduct deburring pressing by a suitable tool so as to flatten the portions of the inner surface of the inner core 12 as shown in FIG. 3(f). Thus, the inner core and the outer shell of the torque converter have toroidal forms, and slits for mounting the blades have to be formed in such toroidal structures with the result that burrs are left on the inner surface of the inner core or the outer shell. These burrs, if left unremoved, will form metal chips which will undesirably be introduced into the hydraulic circuit of the transmission so as to cause troubles such as sticking of a valve. Processing by press on a surface having three-dimensional curvatures, as is the case of the deburring pressing operation in FIG. 3(f), encounters a problem in that the pressing tool may fail to closely and uniformly contact the surface to be pressed. In consequence, the deburring process shown in FIG. 3(f) may result in a non-uniform removal of the burrs. Thus, the pressing of a surface having three dimensional curvatures is difficult to conduct. The pressing of a surface having three dimensional curvatures also encounters a problem in regard to difficulty in precisely holding the die which cooperates with the pressing tool.
In order to obviate these problems, a high degree of skill or experience has been required, as well as a long processing time.